Reinforcement for rubber tires

ABSTRACT

A mat comprising non-woven metal fibers entangled with one another in the form of a cohesive mass, said mat having at least a portion of the pores thereof filled with rubber, a tire reinforced with a mat comprising non-woven metal fibers entangled with one another in the form of a cohesive mass, preferably having at least a portion of the pores thereof filled with rubber and having the fibers bonded together with a bonding agent such as a vulcanized mixture of butadiene, styrene, vinyl pyridinelatex and resorcinol resin; the mat of nonwoven metal fibers suitably contains steel fibers with natural or synthetic fibers.

United States Patent Heling et al. July 22, 1975 [54] REINFORCEMENT FOR RUBBER TIRES 3.221812 12/1965 Barrett .7 152/361 DM 3,690.364 9/1972 Barassi ct al. t, l52/36l DM [751 lm'emorsl 3,763.912 10/1973 Bcrgomi ct al. 152/36! DM Bensheim-Auerbach; Rudolf 1 22: 2 wemhclm both of Primary E.\'aminerDrayton E. Hoffman y Attorney. Agent, or Firm-Burgess Dinklage & [73] Assignee: Firma Carl Freudenberg, Sprung Weinheim, Germany [22] Filed: Dec. 21, 1972 [57] ABSTRACT [21] Appl. No.: 317,337 A mat comprising non-woven metal fibers entangled with one another in the form of a cohesive mass. said mat having at least a portion of the pores thereof filled [3O] Forelgn Apphcatmn Pnonty Data with rubber, a tire reinforced with a mat comprising 1971 German) 3164667 non-woven metal fibers entangled with one another in the form of a cohesive mass, preferably having at least 5 Cl 152/357; 152/355; 152/361 DM a portion of the pores thereof filled with rubber and [51] Int. Cl. B606 9/16; 1360C 9/18 having the fi bonded together i a bonding [58] held of 152/357 agent such as a vulcanized mixture of butadiene. sty- 152/209 355 rene, vinyl pyridine-latex and resorcinol resin; the mat of nonwoven metal fibers suitably contains steel fibers i 1 References Clted with natural or synthetic fibers,

UNITED STATES PATENTS 8 Cl 3 D F 3.l33.583 5/1964 Dobson 152/361 DM 'awmg gums /'TRE V V STEEL 4 1 REINFORCEMENT RUBBER TIRES BACKGROUND OF THE INVENTION 1. Fieldof the Invention Thisinvention relates to the reinforcement of rubber tires. Moreparticularly, this invention relates to the reinforcement of rubber tires through use of a mat of non-woven metal fibers suitably containing natural or synthetic fibers. This invention also relates to rubber tires so reinforced.

2. Discussion of Prior Art It is in the prior art to reinforce rubber tires with inserts in the tread, carcass or beads. It is also in the prior art to embed steel cord reinforcements beneath the tread surface of the so-called carcass. As the name implies, this is a cord whose longitudinal threads consist of steel. Thissteelcord is then covered with layers of rubber and pressed together with same. This results in rubber plies which are reinforced internally with steel.

Itis also in the prior art to insert foursuch steel cord plies into radial tires, the longitudinal direction of the different belts being offset at angles of to 25 from one another. By the designs thus described the socalled triangle of forces is created. Research in the SUMMARY or Tl-IEJINVENTION Broadly; this invention contemplates a mat comprising non-woven metal fibers entangled with one another in the form of a cohesive mass, said mat having at least a portion of the pores thereof filled. with rubber.

- In a particularly desirable embodiment this invention contemplates a mat comprising non-woven metal fibers entangled with one. another in the form of a cohesive mass; said mass containing natural and/or synthetic fibers. Preferably, the non-woven mat of metal fibers and natural or synthetic fibers contains a bonding agent therein which secures fibers to one another to form the cohesive mass. Preferably, the mat further contains rubber which fills at least a portion of the pores thereof.

In accordance with the present invention there is provided a mat which can suitably be employed as a ply in the reinforcement of tires. Specifically, it has been found that several plies of non-wovenfabric of this invention can suitably be employed together with tire cords which run longitudinally or radially in a tire whereby to reinforce the same and to provide an improved tran sversefstrength as well as increased riding comfort. The nonwoven mats of the present invention are made of metalfibers having a staple length of between and 100 mm, preferably between 40 and 60 mm. The fiber itself can be of any metal, including metal :alloy. Included within this group are both ferrous and nonferrous metals and their alloys. In particular,

metal mats can be formed of copper, nickel, iron, steel, manganese, magnesium, stainless steel and the like. Generally speaking, the fibers have a thickness between0.05O and 0.3 mm, preferably between 0.08 and 0.2 mm. 'The thickness of the fiber is dependent upon the'nature of the material including its density and crimpability or bendability. The overall thickness of the mat will also influence the thickness of the fibers thereof.

lna preferred embodiment the non-woven mat containsnatural and/or synthetic fibers. These fibers can be present in; an amount between 5 and by weight based upon the entire fiber content of the mat, preferably between l0 and 30%. Suitable fibers for this purpose include polyamide fibers, especially nylon 6 and nylon 6/6, the polyolefins. especially the polyalphaolefins of C to C especiallypolyethylene, polypropylene, polybutene-l and polybutadiene. Other fibers suitable include the thermoplastic fibers such as polyvinyl chloride and the acrylic polymers such as polyacrylonitrile. Similarly, the polyester fibers. especially those heretofore employed as a tire cord. can be used. These include polyesters prepared by reacting or condensing an iso or terephthalic acid moiety with an aliphatic or aromatic polyhydric compound such as ethylene glycol. bisphenol A and the like.

The staple metal fibers employed in the mat are treated by bending the same so as to change the fibers direction by imparting a bend or crimp having an angle of at least 160. Generally speaking, the bend or crimp formed has an angle of between 20 and 160. Preferably there are between one and three crimps per centimeter of length of staple metal fiber. This bending or crimping action is important as the so bent or crimped fibers are ultimately, when formed into the mat, deposited upon a gas-permeable surface wherein a vacuum is applied to the under side.

In a particularly desirable embodiment the mat of f1- bers is treated with a bonding agent. The weight ratio of fibers to bonding agent, also known as binder, is generally in the range of :5 to 50:50. Suitable bonding agents for this purpose include binding agents, which are rubber compatible and serving by this as adhesions agent. I V

Generally speaking, the bonding agent is applied to the mat and the same is thereafter heated to effect vulcanization of the bonding agent. Of course the subsequent treatment of the mat after the bonding agent has been applied thereto will depend upon the specific nature of the bonding agent.

After the bonding agent is applied, the non-woven fabric, suitably of steel fibers, can then be coated on either side, preferably both sides, in a multiple roll calender with unvulcanized rubber strips which are forced into the mesh of the metallic non-woven fabric and fill at least a portion of the pores or voids in the non-woven mat. After the rubber is vulcanized it can be used to reinforce tire c ords and in fact can be used as a tire cord substitute. For instance, after vulcanization, a steel fiber reinforced bond can be obtained which can be used as a steel cord substitute and as a protective insert for the tread in tires. Additionally, the mat can be employed as a conveyor belt.

Thus it has been found that a belt with two plies of steel cord'and two plies of the non-woven fabric described herein, wherein the metal is steel, alone or with synthetic fibers, e.g., polyamide, and bonded with a vinyl pyridinelatex and resorcinol resin, provides an improved transverse strength in a rubber tire not heretofore provided. Additionally, an improved riding comfort is brought about by an insulating action attributable to the non-woven fabric. Tires embodying the nonwoven fabric are characterized by improved road safety due to the greater contact surface of the tire.

If thesteel non-woven fabric is inserted in place of the conventional cord ply between two unvulcanized rubber layers (doughing in the dissolved rubberc'an be forestalled) the rubber is forced through the pores "of the non-woven fabric in the calendering operation t 'ha t' Referring to the drawings herein.

FIG. 1 is a schematic view showing methods by which i the non-woven metal fiber mats are prepared;

FIG. 2-is a cross section through a tire inwhich beneath the tread 11' are steel cord plies I2and 13. Be tween and above thel'attr,a'reinforcing mat manufactured in accordance with Example 1 bel owpis iricorpo rated; and r I FIG. 3 shows an enlarge cross'section of the Lti're bead. At 14 one sees the threads of a steel cord in cross section. The mat l5, ma de in accordance with Example 1, is wrapped about this steel cord in the man'ner described aboyei' l i l I v DESCRlPTION OF SPECIAL EMBODIMENTS j 'The manufacture of a steel or other metal fiber mat is difficult. One might'at first imagine preparing a sliver on a card, as in'the manufacture of textile fiber mats, and then laying a plurality of such slivers one on the other with a cross-laying apparatus, un til aniat of the desired thicknessis' formed It hasibee'n' ifound, however, that thernetal fibers feritangle upon the card clothing, so that the manufacture of a metal itib r mat in this manner is impossible. v

Furthermore," the metal fibers are grather smooth This is a result of their r'nan'ufacture. Fii's t" alafg'e ber of thin wires ofifo rexampl e, 60 .deniers are "spun and then slightly twist dfilie wire thusprdduced cut intopiecesldf, for; eitample, 4 in, length Qn ac countof'the slightaniourit of t'wisflthie individualj'fibers then fall out of thisslmallpieceof wire. They will then be in a'st a te such as is produced when a handfulof nee-. dles are tossed ,.on,to a table. v

Onejmightthink of grasping the pieces of wire with tweezers anddropping them one after the other u'nifornily over a table until a sheet having a thickness of,"

forexa'mple l cm. This sheet formed of pieces of wire might be called a uniform mat, but its strength is virtuallyiriil; since on account of their smoothness and straightriess the fibersare unable to tangle together like, natural and synthetic fibers. Withthe latter an at lea st,

slight entanglement is possible, so that the fleece thus formed would have of itself a'certain stability sufficient, to enable it'to be carried on grids andirnpr egnated with foam between rolls in the manner described, for example, in U.S.Pat. Nos. 2,719,802, an i-2,719,806.

Nowgin orde r to enablethe metal'fiber ma t to have only this much stability ;tostart with t he me tal fibers are given one or more bends by external action, resultmg in coil-like orY z ig-zag shapes. particularly suitable method for formingmats, which pursuant to the pres-x ent invention can be used'to reinforce tires, is disclosed ineopend'ing application Ser. No. 301,543 of Oct. 27, 1972, now abandoned, hereby incorporated hereinbym reference. Pursuant to the method. therein disclosed, a

cohesive mat of non-woven metal fib'e'r s is formed by initially subjecting short staple lengths of metal fibers to a bendingor crimping action. The staple, length .of

crimped "metal' fibe rs 'iir" ultimately de p'ositedon a gaspermeable surface and a :vacuum, applied. to the under side of the surface whereby the bent fibersare entangled together to form a 'coh esive mass. Preferably, are staple "fibers are? prior a; being deposited: on the gas-permeable surface, p'assed betwe'eh the nip of a spiked roller and a generally horizontal endless conveyor lielt. The purpose of thespikegl r'o lle r'iisto compress and conderic'e'the'fibers. Thereby thearea'weight of the fibers increases before they enter a subsequent nip. The spiked roller suitably has spikesdf a len'gth between and '60 which spikes are i'nse'rt edinto the roller surface at an angle between and 90. i

I The so'processe'd staple metal fibers then pass be tween the nip of a roller and an arcuate surfaee having the 'samecontoiin-as the roll-eri Thehipds' so'dimensionedltha t apressure between '10 and "40'poun ds per square inch'is applied to the staple" metal fibers-passing between the rollerand the opposed contoured'siirfacel The compacteda'nd d'ensified fibers" are th'err'dire'ct ed to a space definedthe roll'e'r a'n'd-an opposed toothed wheel rotating in a direction opposite tothat of the r'oller. lt-"i's this toothed' wheel whichfimparts the desired j Thereafter, the-fibers can suitably Flue conveyed through'use of a generallyvertical pheumatic conveyorchute on asurface which isgas-per'meable'. Generally, they are pneumatically conveyed at a rate between 2 and Y30 meters p er..s e cond, preferably between 10 and ZOfThey strike the gas-permeable surface with great farce.- Negative pressure is maintainedat the under side of thegas-p'ermeable' surface so that the fibers are intimately drawn together andentangled. Entanglement is possible because of the p'i'eviotis bendingand crimping treatment 'towhiclri'the metal fibers;have been subjectedISuitably the gas-permeable surface-canbe' in the form of a cohesive mass, i.e.-, when the ends of' the mat are pulled, themat does not readily comegapart duetto theentanglementof the fibers withone another within themat. i-ZY- .J u: 1 T

Referring-to FIG. 1, an advantageous bending canbe First the smooth fibers arethrown onto a conveyor belt 3 continuously circulating around the.rollsl and 2. Directly behindroll 2, at a'very short distance. there from, a brake shoe-like-block'4' is disposed. .Betweenthe :brake sho,e4 and the roll 5 there is only; a.:narrow.= gap. ,The mat lyingv on the conveyor belt'3.is carried into this r gap between componentsA; and 5. .Since the gap 'is very-narrow, a. pressure is exerted on the-steelmat.'lt is therefore picked upwardly ;to'-the right by the roll turningin the-diree tion ot,-the arrowr: To facilitate entrainment, the rollfimayalso hayea fluted surface,

, thereis provided the toothed r0ll 6 which rotates conthe fibers is generally between 20 and 10f) mm, The 1 trary to the direction of roll 5. The smooth fibers're ach ing the' 'upper end ofthe brake-shoe 4 pass into the :teeth of roll 6 where they are bent one or more times. Bent fibers then drop into the slantingl-y disposed passage 7.'At the vsame tirne a strongcurrent of air is deliv "ered ;into this passage from 8. The bent fibers-are thus carried=in a stream .of air toa perforated roll 9 in whose Hinteriof a vacuum prevails. On the surface of .the roll 9 there no'w'formsfa uniform mat in which thefibers-are curled, bent and entangled with one another. One quarter to half a revolution of the perforated roll 9 later this mat has again left the surface of same and passes onto the conveyor belt 10. Additional working can be performed by methodsof the prior art. It is possible, for example, to spray a binding agent into the metal mat. On account of the open structure a uniform distribution of the binding agent takes place within the mat.

The mat can then have its pores filled, at least in part, with unvulcanized rubber. The amount of rubber would generally be between 50 and 95% by weight, based upon the weight of the untreated finished fibrous mat. Thereafter the unvulcanized rubber is subjected to vulcanizationwhieh provides vulcanized rubber in the fibrous mat in an amount between 50 and 95% by weight, based upon the weight of the finished rubbercontaining mat.

As indicated above, the fibrous mat can be initially treated with a bonding agent. Suitably, the bonding agent is a mixture of butadiene, styrene, vinyl pyridinelatex and resorcinol resin. This mixture can have a composition within the following ranges:

Component Broad Preferred Butadiene 40 to 60 100 to I50 Styrene 10 to 30 25 to 75 Vinyl pyridine-latex 20 to 30 50 to 75 Resorcinol resin to 30 35 to 75 Composition of the mixture Weight parts Weight parts of Aqueous form dry substance Bunatex VP, 40% solution 250 I00 Vulkadur T, 40% solution 50 Formaldehyde solution. 30% 20 6 Condensation water or 310 distilled water In the end product the ratio of fiber to binder is 20. This non-woven fabric is then rubberized on both sides in a multiple roll calender with unvulcanized rubber at a weight of 500 g/m each side. The'unvulcanized rubber completely penetrates into the pores and meshes of this mat, so that after the vulcanization of the rubber a fiber-reinforced band has developed, which may be used as a substitute insulating insert and steel cord, as a stiffening bead insert, or as a conveyor belt core material. i

As stated above, natural or synthetic fibers can be present in the non-woven fabric. These fibers suitably have a staple length between 20 and l20 mm and a denier of between 6 and 40.

The mat employed in the tires can suitably have a thickness between I and 5 mm, preferably between 2 and 3 mm. It can have between 20 and metal fibers per cm What is claimed is:

l. A tire comprising a thread and a carcass portion, said carcass portion reinforced by a non-woven mat, said mat comprising randomly disposed linearly deformed metal fibers entangled with one another in the form of a cohesive mass, said metal fibers being in the form of staple fibers having a staple length up to 100 mm. and a thickness of 0.05 to 0.3 mm, said mat having pores between said metal fibers through the thickness of said mat, said pores containing rubber.

2. A tire according to claim 1 wherein the pores of said mass are filled with unvulcanized rubber.

3. A tire according to claim 2 wherein, in addition to said unvulcanized rubber, said mat contains a bonding agent.

4. A tire according to claim 2 wherein the metal of said metal fibers is steel.

5. A tire according to claim 4 which comprises a plurality of steel cords and a plurality of said mat.

6. A tire according to claim 5 comprising two plies of steel cords and two plies of said mat comprising nonwoven metal fibers entangled with one another in the form of a cohesive mass.

7. A tire according to claim 6 wherein at least a portion of the pores of said mat are filled with unvulcanized rubber.

8. A tire according to claim 5 wherein at least a portion of the pores of the mat are filled with unvulcanized rubber such that the weight percent of rubber in the mat is between 50 and by weight. 

1. A tire comprising a thread and a carcass portion, said carcass portion reinforced by a non-woven mat, said mat comprising randomly disposed linearly deformed metal fibers entangled with one another in the form of a cohesive mass, said metal fibers being in the form of staple fibers having a staple length up to 100 mm. and a thickness of 0.05 to 0.3 mm, said mat having pores between said metal fibers through the thickness of said mat, said pores containing rubber.
 2. A tire according to claim 1 wherein the pores of said mass are filled with unvulcanized rubber.
 3. A tire according to claim 2 wherein, in addition to said unvulcanized rubber, said mat contains a bonding agent.
 4. A tire according to claim 2 wherein the metal of said metal fibers is steel.
 5. A tire according to claim 4 which comprises a plurality of steel cords and a plurality of said mat.
 6. A tire according to claim 5 comprising two plies of steel cords and two plies of said mat comprising non-woven metal fibers entangled with one another in the form of a cohesive mass.
 7. A tire according to claim 6 wherein at least a portion of the pores of said mat are filled with unvulcanized rubber.
 8. A tire according to claim 5 wherein at least a portion of the pores of the mat are filled with uNvulcanized rubber such that the weight percent of rubber in the mat is between 50 and 95% by weight. 